A headrest is known from DE 102 36 259. It has a cushion support mounted on support rods attached to the seat back so as to pivot about a pivot axis. The cushion support may be pivoted between a use position and a stowage or non-use position. In the use position the cushion support forms an upright support surface for the head of the vehicle occupant, and in the stowage position the cushion can be dropped and nested against the top of the seat back. By pivoting the cushion support of a headrest in the rear seat of a vehicle into the stowage position, the driver has better visibility through the rear window when no passengers are in the vehicle.
The headrest may be latched in the use position to prevent unintended pivoting of the cushion support. The headrest may be unlatched by pressing on an actuating bar, thereby shifting a latch element in a translational or straight-line movement from the latched or holding position in which the headrest cannot pivot to the released or freeing position in which the headrest cannot pivot about its horizontal axis.
Another headrest is described in DE 20 2004 004 251 where the cushion support is pivoted on a support bow and may be latched in a use position and a stowage position. A latching pin displaceable in a straight-line manner longitudinally of its axis is mounted on the cushion support. An end of the latching pin has an tip can fit in recesses in a latching disk attached to the support bow. The latching pin may be moved out of the recess in the latching disk in a straight-line manner by pressing an actuating button, thereby releasing the latch and allowing the cushion support to pivot.
A principle problem with both of these systems is that, in a crash, it is possible that the vehicle will be subjected to a sudden acceleration or deceleration in a direction parallel to the actuation direction of the latch element. This will unlatch the cushion support so it can pivot into a position in which it either offers no more meaningful bracing of the passenger's head, or even into a position where it is hazardous when, for instance, the passenger rebounds against it.